Recovery of bitumen from tar sands utilizing an evacuation step



June 30, 1964 R. A. HEMSTOCK 3,139,397 RECOVERY OF BITUMEN FROM TAR SANDS UTILIZING AN EVACUATION STEP Filed O01;w 6, .1961

8 tSAND-WATER Russell A. Hemsrock inventor By U,

Potent Attornev United States. Patent 3,139,397 RECOVERY OF EITUIVEN FROM TAR SANDS UTILIZING AN EVACUATION STEP Russell A. Hemstock, Calgary, Alberta, Canada, assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Oct. 6, 1961, Ser. No. 143,404 5 Claims. (Cl. 208-11) The present invention is broadly concerned with the efficient recovery of hydrocarbons from tar sands. The invention is more particularly concerned with an improved technique of efficiently removing hydrocarbons, such as bitumen, tars, and the like, from tar sands containing the same, utiizing a particular technique involving a vacuum separation step. The present invention is more particularly concerned with the eflicient recovery of hydrocarbons from tar sands such as Athabaska tar sands.

In various areas of the World, tar sands exist which contain various types of hydrocarbons as, for example, the heavy deposits of Athabaska tar sands existing in Canada. These sands contain tremendous reserves of hydrocarbon constituents. For example, the oil in the sands may vary from about 5% to 21% by weight, generally in the range of about 12% by weight. The gravity of the oil ranges from about 6 to 10 API, generally about 8 API. These sands may lie from zero to several hundred feet below an overburden and the beds may range from about 100 to 400 feet thick. A typical oil recovered from the sands has an initial boiling point of about 300 F., 1.0% distilled to 430 F., 20.0% distilled to 650 F. and 50.0% distilled to 980 F. However, the recovery of hydrocarbons in the past has not been effective to any great extent due to the deficiencies in operating techniques for the recovery of these hydrocarbons. For example, a relatively small amount of clay (from about to 30%, usually about in the sand greatly retards recovery of the oilutilizing conventional water techniques. Apparently the oil and the clay from skins which envelop small pockets of water often containing finely divided sand; then the enveloped pockets are distributed in water, thus forming a type of emulsion.

Numerous attempts have been made in the past to recover bitumen from the Athabaska tar sands in various manners. For example, it has been suggested that a solvent be added in order to reduce the viscosity of the bitumen, and in conjunction with water, to float the bitumen solvent mixture away from the sand. Although this The present invention may be readily understood by reference to the drawing illustrating one embodiment of the same. Referring specifically to the drawing, tar sands.

as mined are introduced into'a shearing-mixing stage 1 by means of feed line 2. Water is introduced into line 2 and mixed with the sands by means of line 3. The water may be introduced directly into mixing-shearing zone 1.

It is also to be understood that, while only one mixing zone is illustrated, a plurality of shearing-mixing zones may be used and a plurality of injection points also utilized.

. The mixing operation in zone 1 is carried-out under conditions wherein a shearing-thrust isir'nparted -to the sands being mixed with the added water. Under theseconditions, substantially oil-free sands separate and the entire mixture is then passed into a second stage orzone 5 by means of line 4. In accordance with thepresent invention, additional water is introduced'into zone 5 by means of line 6 while thezone is maintained under a vacuum by means of line 7. Under these conditions, sand and water separate and fall to the bottom and are removed by means of line 8. An oil phase forms in the 7 same.

EXAMPLE 1 A 100 g. of a sample of tar sands (dry basis) containing7 wt. percent connate water and 13 wt. percent oil was mixed with 30 wt. percent water for half a minute to effect disintegration of the tar sands into sand and very small oil particles distributed in water. This was carried out at F. The mixture was transferred to a flask containing excess water and the pressure was reduced. When the pressure reached 200 mm. of mercury, oil floated to the surface. At lower pressure, increasing amounts of technique achieves a good separation of clean sand, the

addition of water results in problems with the formation of stable emulsions and sludges which have been very diflicult to separate. Thus, extensive supplementary processing has been required in order to avoid large oil losses.

It has also been suggested in the past that tar sands as they are mined be handled by a thermal process in order to recover the bitumen therefrom. However, this process has been uneconomical due to the large amount of heat which is lost due to the fact that the heat is imparted to the sand and cannot be effectively and efficiently recovered therefrom. It has been suggested for example that tar sands be handled in a direct fluid coking operation.

However, as pointed out, this process is uneconomical for the reasons given above. Also, any process that will effectively handle tar sands must have the ability to handle a very wide range of tar sand and compositions which occur even in an immediate location. Some processes as, for example, direct fluid coking are able to handle these widely different compositions and, in accordance with the present process, employing a two-phase operation wherein in an initial phase a substantially richened tar sand is produced and wherein in the second phase the enriched sand is for example handled in a fluid coker, surprisingly effective results are secured.

oil floated to the surface. Complete separation was obtained, with clean sand remaining at the bottom of the vessel, in less than half a minute from starting the evacuation.

It was observed that the very small oil particles that floated to the water surface immediately coalesced, forming large agglomerates, hence reducing the'water content of the oil mass. These large oil agglomerates were skimmed off the surface of the water.

EXAMPLE 2 The sand reduction in this operation can be compared with that from mixing with water and mechanical separation. This is shown inthe following table:

Table 1 GOOD SAND REDUCTION IS ACOOMPLISHED AT LOWER TEMPERATURES AND WITH LOWER AMOUNTS OF IN PREMIXING AND MINIMUM PREMIXING [Tar sands contained 7 wt. percent water, 13 wt. percent oil] 1 On tar sands (dry basis). 2 Also contains oil not recovered in oil phase. 8 Use of mechanical separation at atmospheric pressure.

From the. above it is apparent that a better oil recovery is secured in a shorter time period when utilizing a vacuum separation technique.

EXAMPLE 3 In' operation A a mixing time of one minute was employed with a pressure of 200 turn. of mercury absolute. Under these conditions, about 65% of the sand was removed wherein the oil phase comprised 45% of oil.

In a similar Operation B, atmospheric. pressure was employed and a mixing time of 5 minutes utilized. Under these conditions, about 50% of the sand was removed wherein the oil phase comprised about 33%. Thus, from the above it is apparent that the use of vacuum increases substantially the extent to which oil may be recovered.

The pressure utilized is below atmospheric, preferably in the range from 50 to 200 mm. of mercury absolute. In accordance with the present operation, the temperature may be atmospheric or may be in the range from 32 to 160-F.

It is felt that the desirable results of the present invention are secured due to the fact that the excess void volume in the tar sands that is not filled with oil and water is filled with 'gas. Some of the gas was dissolved in the oil. The presence of this gas in the-tar sands is made to efiect separation of an oil phase from sand in water at low temperatures.

What is claimed is:

1. Improved process for producing enriched bitumen tar sands from natural tar sands which comprises adding a fluid comprising water to natural sands and subjecting the mixture to a mixing-shearing action at a temperature in the range from about F. to about F thereafter subjecting the mixture to a vacuum in the range from about 50 to 200 mm. of mercury absolute, and at a temperature in the range from about 32 F. to about 160 F. wherein substantially bitumen-free sands separate from enriched bitumen sands, thereafter separating said enriched bitumen sands from the substantially bitumen-free sands;

2. Process as defined by claim 1 wherein about 40% to 500% by weight, based upon dry bitumen sands, of water is added to said natural sands.

3. Process as defined by claim 2 wherein the temperature is maintained in the range-from about 32 to about F. v

4. Process as defined by claim 2 wherein the quantity of water added is in the range from about 40% to about 5. Process as defined by claim 1 wherein the connate water content of said natural sands is from about 4% to 12%.

References Cited in the fileof this patent UNITED STATES PATENTS Canada Mar. 20, 1956 

1.IMPROVED PROCESS FOR PRODUCING ENRICHED BITUMEN TAR SANDS FROM NATURAL TAR SANDS WHICH COMPRISES ADDING A FLUID COMPRISING WATER TO NATURAL SANDS AND SUBJECTING THE MIXTURE TO A MIXING-SHEARING ACTION AT A TEMPERATURE IN THE RANGE FROM ABOUT 50*F. TO ABOUT 90*F., THEREAFTER SUBJECTING THE MIXTURE TO A VACUUM IN THE RANGE FROM ABOUT 50 TO 200 MM. OF MERCURY ABSOLUTE, AND AT A TEMPERATURE IN THE RANGE FROM ABOUT 32*F. TO ABOUT 160*F. WHEREIN SUBSTANTIALLY BITUMEN-FREE SANDS SEPARATE FROM ENRICHED BITUMEN SANDS, THEREAFTER SEPARATING SAID ENRICHED BITUMEN SANDS FROM THE SUBSTANTIALLY BITUMEN-FREE SANDS. 